The present invention relates to automatic transmissions and, more particularly, to a replacement throttle valve cable assembly for General Motors GM 4L60, GM3T40, GM4T60, THM 200, THM 325-4L, and THM 200-4R (hereinafter “GM transmissions”).
Automotive vehicles with carbureted engines utilize a throttle valve cable, which attaches to the throttle valve linkage at one end thereof and is connected to a throttle valve control lever on the transmission housing. The throttle valve (hereinafter “TV”) cable is routed from the throttle body in the engine compartment under tension passing through a cable housing and bends to conform to mounting brackets located on the engine and transmission to be secured on the throttle valve of the transmission.
The length of the TV cable is critical to proper shift performance. If the TV cable is shortened, both line pressure and shift points will be raised. Alternatively, if the TV cable is lengthened, both line pressure and shift points are lowered. Operating the vehicle with a longer TV cable causes premature clutch wear and other transmission malfunctions.
The TV cable is subject to mechanical wear and fraying and must eventually be replaced at periodic maintenance intervals. At present the original equipment manufacture for the GM transmissions provides the throttle valve cable only in a predetermined length in a complete assembly, which requires the replacement of otherwise serviceable components such as the cable housing and linkage clip along with the TV cable. This involves significant replacement costs for the vehicle owner when repair of the TV cable is necessary. Many vehicle owners would like to override the predetermined factory setting of the throttle valve cable, tailor the shift points or shift feel of the vehicle, and reduce related service and labor costs.
There are known prior art patents that are available in the field of throttle valve cables and cable fittings and their discussion follows. One example of a prior art throttle valve cable is disclosed in U.S. Pat. No. 5,638,721 to Lee and also in U.S. Pat. No. 5,727,425 to Lee, which teach a method and apparatus for adjusting a throttle valve cable in an automatic transmission. In these patents a sleeve and spring are installed at the distal end of the throttle valve cable between the cable end clamp and the tear-drop shaped cable end fitting on the throttle valve cable. The spring opposes movement of the cable end fitting toward the distal end of the throttle valve cable so that the cable end fitting is at its maximum distal position only at fully open throttle. This gives the vehicle operator the shift feel of a shorter throttle valve cable at most throttle openings. The sleeve and spring are installed only on throttle valve cables in automatic transmissions that do not have throttle valve cable end fittings permanently attached to a throttle cam.
An example of a throttle cable fitting structure is shown in U.S. Pat. No. 5,046,380 to Matsumoto et al. which discloses a throttle valve operating cam of an automatic transmission and an output control member of an automotive engine interconnected so as to cooperate with each other by a cable consisting of an outer tube and an inner cable.
Another example of a cable adjustment device for an automotive throttle body is shown in U.S. Pat. No. 5,295,408, to Nagle et al. which discloses an adjustable cable strand end fitting for use in adjusting the slack or tension in a cable strand attached through the fitting to a throttle body moveable member.
U.S. Pat. No. 5,174,170 to Kato et al. and U.S. Pat. No. 4,869,123 to Stocker disclose cable length adjustment and cable position control devices, which may be considered relevant to the present invention.
While these devices fulfill their respective, particular objectives and requirements, the aforementioned patents do not disclose the throttle valve cable assembly including the cable adjustment stud of the present invention, which substantially departs from the conventional concepts and designs of the prior art.